Chemistry Lab 124 - University of Dayton - Exam 1 Questions And Answers With Verified Study Solutions

Analytical Balance - 5 sig figs or 4 if unstable and a line over the 4th digit Thermometer - Three sig figs (20.5) graduated cylinder (50mL) - 3 Sig Figs (50.2) Graduated Cylinder (10mL) - 4 sig figs (10.25) volumetric flask - 5 sig figs Buret - 4 sig figs (27.22) Pipet - 4 sig figs (.02500L) adding and subtracting sig figs - least number of decimal places added or subtracted - 12.2 + 5.44 = 17.6 multiplying or dividing sig figs - the least number is the number of sig figs you can have in the answer - 3.3 x 2.55 = 7.425 = 7.4 Qualitative Analysis - Identification of an unknown compound precipitate - A solid that forms from a solution during a chemical ard solution - the solution that contains the precisely known concentration of a solute Supernatant - liquid remaining after the precipitate has settled Preparation of a Volumetric Solution - 1. Mass Compound on weigh dish 2. Transfer to a 100mL V.F. - Rinse all compound into the flask w DI water 3. Add addition di water to fully dissolve the salt and get to the line 4. Transfer salt to a 250 mL beaker 5. Wash Flask and lid w soap and water Titration - slowly adding one reactant to another, and measuring how much is needed for the subsequent reaction to be completed Titrant - Base being slowly added Analyte - Acid being analyzed Stoichiometric/Equivalence point - When the analyte is completely neutralized Endpoint - point at which the indicator changed colors Indicator error - Difference between the endpoint ant equivalence point standardization - analytical determination of the molarity of the solution Primary Standard - a substance of very high purity which is stable in airPrecision - how close the results of the trials are to one another Outliers - extreme values that don't appear to belong with the rest of the data Accuracy - How close a experimentally determined value is Calculation of molarity in a titration - 1. mass/molar mass = moleKHP 2. mole (1mole/1mole) = moleNaOH 3. mole/vol NaOH L= molarity NaOH Lattice Points - The points on a coordinate grid where the grid lines intersect. Interstital site - Non-filled portion of the unitcell coordination number - number of atoms or ions surrounding an atom or ion in a crystal lattice Total Equivalent atoms - Cordination number of an interstitial site - number of atoms immediately surrounding it Primitive Cubic Model - 8 atoms 1/8 fraction 1 total equivalent atom Coord Num = 6 body centered cubic - 2 total equivalent atoms 8 coordination numface centered cubic - 12 coordination number 4 total equivalent atoms 4 atoms surround the interstitial site Coordination number of the site is 6 Tetrahedral site - 4 coord num